Known engine control systems have utilized various engine parameters to control engine ignition timing. For example, known systems have utilized exhaust gas recirculation (EGR) rate tables, barometric pressure tables, and air-fuel tables to adjust ignition timing. However, each of these engine parameters has been treated independently when controlling ignition timing leading to complex control methods. Thus, for example, if the barometric pressure communicating with a vehicle changes, the effect of the barometric pressure change on a desired or target value for an engine parameter, such as an EGR rate, may be unknown. Thus, an EGR based adjustment to ignition timing that was not calibrated for varying barometric pressure might result in non-optimal ignition timing. Similarly, a barometric pressure based adjustment to ignition timing would not-include the effect of EGR changes. Thus, all these tables might not provide optimal adjustment of ignition timing for varying barometer and EGR conditions.
In an attempt to lessen the impact of previously mentioned problem, automotive manufacturers have calibrated vehicles for either high altitude operation or low altitude operation. A high altitude vehicle may utilize a barometric pressure table to control ignition timing while shutting off EGR, or not use an EGR table for ignition timing adjustment. Thus, a high altitude vehicle may not perform optimally at sea-level when EGR may be desirable. Similarly, a low altitude vehicle utilizing an EGR table may not perform optimally at relatively high altitudes because the affect of barometric pressure on the EGR table may be unknown.
The inventor herein has recognized that there is a need for a simpler and more integrated system and method for controlling ignition timing.